Potentiometric and thermal studies of a coated-wire benazepril-selective electrode

A coated-wire benazepril-selective electrode based on incorporation of the benazepril-tetraphenylborate ion pair in a poly(vinylchloride) coating membrane was constructed. The influences of membrane composition, temperature, pH of the test solution, and foreign ions on the electrode performance were investigated. The electrode showed a Nernstian response over a benazepril concentration range of 1.26 x 10(-5) to 0.58 x 10(-2) M, at 25 degreesC, and was found to be very selective, precise, and usable within the pH range 2.5-9.2. The standard electrode potentials, E degrees, were determined at 20, 25, 30, 35, 40 and 45 degreesC, and used to calculate the isothermal temperature coefficient (dE degrees /dT) of the electrode. Temperatures higher than 45 degreesC seriously affect the electrode performance. The electrode was successfully used for potentiometric determination of benazepril hydrochloride both in pure solutions and in pharmaceutical preparations. (C) 2002 Elsevier Science B.V. All rights reserved.